Before a seizure, many people experience distinct warning signs that fall into two phases: a prodrome that can begin hours or days in advance, and an aura that strikes seconds to minutes before the seizure itself. Not everyone gets these warnings, but recognizing them can provide critical time to get safe.
Two Phases Happen Before a Seizure
Seizures unfold in four stages: prodrome, aura, the seizure itself (called the ictus), and recovery (the postictal phase). The first two stages are the “before” period, and they feel quite different from each other. The prodrome is a slow shift in mood or energy that builds over hours or days. The aura is a sudden, vivid sensory experience that signals a seizure is imminent or already beginning in a small part of the brain.
Think of it this way: the prodrome is like seeing dark clouds on the horizon, while the aura is hearing the first crack of thunder.
The Prodrome: Hours to Days Before
About 20% of people with epilepsy notice changes in how they feel well before a seizure happens. These shifts can appear hours or even days in advance and are collectively called the prodrome. The most common prodromal symptoms are anxiety, irritability, confusion, headache, tremor, and sudden mood swings like unexplained anger or sadness.
Prodromal signs are subtle, which is what makes them tricky. You might chalk up the irritability to a bad day or blame the headache on dehydration. Over time, though, some people learn to spot their own personal pattern. A partner or family member may actually notice the change before the person with epilepsy does, reporting that they seemed “off” or unusually short-tempered in the hours leading up to a seizure.
Because the prodrome is so individual, keeping a seizure diary that tracks mood, sleep, and physical symptoms can help you and your neurologist identify whether you have a reliable warning window.
The Aura: Seconds to Minutes Before
The aura is far more dramatic and recognizable than the prodrome. It’s actually the very beginning of seizure activity in a localized area of the brain, which is why doctors classify it as a focal aware seizure. You remain conscious during an aura, but the experience can be strange and difficult to describe afterward.
Auras are more common than most people realize. A study published in the journal Neurology found that roughly 70% of people with epilepsy report experiencing auras, regardless of whether they have focal or generalized epilepsy. The specific sensation you feel depends on which part of the brain the electrical activity starts in.
What Auras Feel Like
The range of aura experiences is wide, but several types come up repeatedly:
- A rising feeling in the stomach. This is one of the most commonly reported auras. People describe it as a wave or flutter that moves upward from the abdomen toward the chest and throat, similar to the drop on a roller coaster but without any external cause.
- Déjà vu. An overwhelming, eerie sense that you’ve lived through this exact moment before. It’s more intense than the casual déjà vu most people experience occasionally.
- Unusual smells or tastes. Some people smell something burning or chemical-like that no one else can detect. Others get a sudden metallic, bitter, or acidic taste in their mouth.
- Sudden intense emotion. A wave of fear, joy, or dread that arrives without any obvious reason and feels disproportionate to what’s happening around you.
- Visual disturbances. Flashing lights, colored spots, or seeing things that aren’t there.
- A wave through the head. A strange sensation that’s hard to articulate, often described as a ripple or pulse moving through the skull.
- Body distortions. A feeling that an arm or leg is suddenly much bigger or smaller than it actually is, or numbness and tingling in one part of the body.
Some people find their auras nearly impossible to put into words. They report feeling “strange” during the event but struggle to explain it after. This is normal and doesn’t mean the experience wasn’t real or useful as a warning sign.
What’s Happening in the Brain
In the minutes before a seizure, the brain is already changing in measurable ways, even before a person feels anything. EEG recordings show that electrical activity across the brain increases progressively as a seizure approaches. This isn’t limited to the spot where the seizure starts. One study using detailed brain wave analysis found that activity increased across multiple brain regions, with power rising between 6% and 22% in standard frequency bands. Higher-frequency bursts increased even more dramatically.
The buildup tends to be gradual rather than sudden, with slow brain waves (the kind associated with drowsiness and deep processing) showing a steady, linear climb in the period before the seizure begins. There are also chemical shifts: in the seconds before onset, the brain’s local environment becomes slightly more alkaline, which can trigger rapid oscillations that tip the balance into a full seizure. These changes explain why the aura feels the way it does. Your brain is already misfiring in a small area, producing real sensory and emotional experiences before the electrical storm spreads.
Triggers vs. Warning Signs
It’s worth separating what happens before a seizure from what causes one. Triggers are external or behavioral factors that lower the seizure threshold: sleep deprivation, heavy alcohol use, flashing lights, missed medications, high stress, illness, or hormonal changes. Warning signs, by contrast, are the symptoms your brain and body produce once a seizure is already building.
Sometimes these overlap. You might notice that your prodromal irritability gets worse when you’re sleep-deprived, or that your auras are more frequent during periods of high stress. Tracking both triggers and warning signs separately gives you the best picture of your seizure patterns.
What to Do When You Recognize a Warning
If you feel an aura coming on, you have a narrow but valuable window to protect yourself. The most important step is getting to a safe position. If you’re standing, sit or lie down on the floor. Move away from stairs, sharp furniture, water, or traffic. If other people are nearby, let them know what’s happening so they can stay with you and time the seizure if it progresses.
For people around someone having a seizure, the CDC recommends clearing the area of anything that could cause injury, gently easing the person to the ground if they’re falling, and turning them on their side with their mouth pointing toward the ground to keep the airway clear. Place something soft under their head, remove eyeglasses, and loosen anything tight around the neck. Time the seizure. If it lasts longer than five minutes, call 911.
Wearable Devices and Seizure Prediction
Technology is beginning to catch up with what the brain does before a seizure. Wearable devices, primarily wristbands that track heart rate, skin conductance, and movement, are shifting from detecting seizures as they happen to predicting them before they start. The goal is to identify the physiological changes that precede a seizure and alert the wearer in time to get safe or take preventive action.
This field is still developing. One study using a wrist-worn sensor combined with clinical data was able to predict whether a seizure would occur within the next day with about 66% accuracy. That’s not reliable enough for clinical use yet, but researchers are working on combining multiple signals, including sleep patterns and longer monitoring windows, to improve performance. For people who don’t get clear auras or prodromes, these devices may eventually fill the gap.